1. Field of the Invention
The present invention relates generally to a buckle used for joining a belt incorporated in clothes, baggages, canteens and so forth and particularly to such a buckle equipped with a lock member for locking a plug and a socket of the buckle in coupled disposition.
2. Prior Art
A typical buckle of the type described is disclosed in Japanese patent laid-open publication No. 4-221502. This disclosed buckle generally comprises a plug having a pair of parallel resilient arms, a socket being in the form of a rectangular casing for receiving the arms and having a pair of openings one formed in each side thereof. Each arm has a prong on its tip and each side opening has a coupling edge. As the arms of the plug is inserted into the socket, the arms first are compressed toward each other against their resiliency and, as soon as the prongs reach the openings, the arms are restored to its original shape under their resiliency to thus bring the prongs into coupling engagement with the coupling edge. The buckle further includes a lock member. The lock member is mounted on one side of the socket so as to reciprocally move between a locking position where the prongs of the arms of the plug are restrained from coming out of coupling engagement with the opening edge of the socket and an unlocking position in which the plugs are allowed to come out of engagement with the opening edge. The locking member has a pair of juxtaposed recesses formed on its rear side. A resilient cantilevered tongue with a locking detent at its distal end is provided on said one side of the socket. The locking detent is normally urged under the resiliency of the resilient cantilevered tongues against the rear side of the locking member for locking engagement with the recesses on its rear side; the locking member is set relative to the socket such that, when the detent comes into locking engagement with one recess, the locking member is in the locking position and when the detent comes into locking engagement with the other recess, the locking member is in the unlocking position.
However, this buckle suffers from drawbacks. The locking of the locking member is effected by a unidirectional bias exerted by the resilient cantilevered tongue so that the locking member is susceptible to come off the locking position accidentally. Furthermore, the bias of the resilient cantilevered tongue provides an increased frictional resistance which makes sluggish the reciprocation of the lock member on the socket.